It has previously been discovered that electrical devices including electrochemical cells can be constructed using the technology of the aerosol industry. This discovery is set forth in U.S. Pat. Nos. 4,136,438 and 4,052,537 issued on Jan. 30, 1979 and Oct. 4, 1977, respectively, to the same assignee as the instant application and incorporated herein by reference.
Aerosol type cells are formed by placing an electrochemical cell system, including an anode and a cathode, into a cell can having an open end and introducing an electrolyte solvent and/or liquid depolarizer into the cell. The rim of the open end of the cell can is rolled inwardly into the shape of a torus. A cover having a lip portion that conforms generally to the shape of the torus is crimped radially outwardly beneath the torus to hold the cover on the end of the can and to seal the cell. An insulating material, disposed over the underside of the lip portion prior to crimping, insulates the cover from the can in the completed cell.
Aerosol technology has been found to be particularly well suited for manufacturing cells containing a pressurized, normally gaseous, liquefied electrolyte solvent and/or liquid depolarizer due to the many similarities between the physical properties of the preferred electrolyte solvent and/or liquid depolarizer (i.e. sulfur dioxide (SO.sub.2)) and the propellants generally used in aerosol devices. Both types of materials are gases at room temperature and atmospheric pressure but are mixtures of pressurized gas and liquid within the aerosol container. Both can easily be liquefied by moderate pressure alone, moderate cooling alone or a combination of the two. Both cooling and the amount of pressure required for the liquefication of the electrolyte solvent and/or depolarizer and the aerosol propellants are easily achieved by known equipment. However, problems have arisen in the filling of the cell cans with the pressurized liquid electrolyte and/or liquid depolarizer and in the subsequent capping of the cell cans.
Aerosol devices are generally filled and capped within a sealed chamber. Filling and capping equipment is not usually affected by the aerosol propellants since the generally used propellants (such as fluorinated hydrocarbons, carbon dioxide or low boiling point hydrocarbons) are inert to the equipment used for filling and capping the aerosol cans. Liquid electrolyte solvents and/or liquid depolarizers, such as sulfur dioxide, however, can be corrosive. As a result, the interior of the filling chamber itself and the capping equipment within the filling chamber, which are not affected by ordinary propellants, may be corroded by the liquid electrolyte solvents and/or liquid depolarizers such as the sulfur dioxide used in electrochemical cells.
One method of filling the cell so that the capping procedure can be performed outside of the filling chamber (as disclosed in U.S. Pat. No. 4,052,537) with the capping equipment being removed from the corrosive atmosphere of the filling chamber is by chilling the gaseous electrolyte solvent and/or depolarizer material until it is a liquid and filling the container with the chilled liquid. Since the cold liquid electrolyte solvent and/or liquid depolarizer will remain a liquid until its temperature rises above its boiling point and the initial temperature can be controlled so that this temperature is not exceeded during normal filling and capping procedures, capping can be performed outside the filling chamber. A drawback of this method is that once the liquid electrolyte solvent and/or liquid depolarizer is in the cell can, it, without additional cooling, begins to absorb heat from the environment. The warming liquid electrolyte solvent and/or liquid depolarizer may begin to vaporize if capping is not completed with the precalculated time available for filling and capping. Further, the process of using chilled liquid electrolyte solvent and/or liquid depolarizer to fill cell cans requires first chilling and then maintaining the liquid electrolyte solvent and/or liquid depolarizer within the filling apparatus at a sufficiently low temperature to avoid gasification of the liquid therein. Such chilling is expensive, requiring costly equipment and large energy expenditures. Condensation further adds to the complexity and cost of the filling process.